Government workers who sometimes moonlight as writers, speakers or consultants will be watching a U.S. District Court lawsuit that seeks to protect their right to freelance.

At issue is a new law, which goes into effect next month, that outlaws such activities and imposes a maximum $10,000 fine for violators.

The ban (outlined here Oct. 29) is part of the Ethics Reform Act of 1989. It was aimed at limiting congressional honoraria. But Congress extended the sweeping ban on outside income to rank-and-file federal workers. It takes effect Jan. 1.

Many U.S. employees supplement their salaries by writing, lecturing or consulting on subjects ranging from gardening and car repairs to history, music and astrology. Others sometimes take gifts, in lieu of payment, for off-duty articles or speeches about particular areas of their expertise that are unrelated to their federal jobs.

Professional groups estimate that thousands of Washington area employees fall into the category of occasional moonlighters who will be affected by the 1991 ban.

The National Treasury Employees Union and two Internal Revenue Service employees filed the lawsuit against the honoraria ban. It contends that the ban violates the First Amendment right of freedom of speech.

One of the employees, Jan Adams Grant, a tax examining assistant in Ogden, Utah, is an environmental writer. The union says she often lectures for pay on the perils of earthquakes.

The other plaintiff, Thomas G. Fishell, of Garland, Tex., is a minister who is sometimes paid to conduct weddings and funerals or deliver sermons.

The honoraria ban apparently does not cover individuals who have employment-type contracts for regularly scheduled writing or lecture assignments. Nor does it appear to cover writers whose earnings come from royalties, government lawyers say.

Many federal employees are talking with their nonfederal employers, and with legal officers in their own agencies, to draft work agreements or contract-type letters that would not violate the honoraria ban.

The law says that "no representative or officer or employee of the government may receive honorarium, which is defined as any money or thing of value, for any speech, appearance or writing, excluding travel expenses. There is no exception for speeches, appearances or writings on matters that are totally unrelated to one's government job."

Members of Congress -- especially those representing the 360,000 Washington area federal workers -- are expected to introduce legislation early next year to roll back or relax the honoraria ban. Just before Congress adjourned in October, there was a move in the Senate to do just that by attaching a legislative rider to a bill naming a post office. But it got caught up in the deficit-reduction vote and the rush to adjourn. Something similar is likely to happen again.

Meanwhile, government employees who write wine columns, act as restaurant critics, lecture on Indian cultures or furniture restoration, or officiate for money or gifts at ceremonies are frantically trying to figure out what the ban means for their off-duty occupations.